Needle-bar mechanism for sewing machines



Q 4, EQ2@ F. F. ZEHER REEDLEBAR MECHNISM FUR SEWING MACHINES 2'sheetsheet -1 Fwede E Zenker Patented Aug. 4, 1942 NEEDLE-BAR MECHANISMFOR SEWING MACHINES Frederick F. Zeier, Fairfield, Conn., assigner toThe Singer Manufacturing Company, Elizabeth, N. J., a corporation of NewJersey Application January 3, 1940, Serial No. 312,230

6 Claims. (C1. 112-206) In practice, it has been found that in known imachines having a needle-feed, wherein the usual needle-bar frame ishung at its upper end upon a stationary fulcrum-stud to vibrate in theline of feed, the needle becomes heated when stitching heavy fabricswith a relatively long stich at high speed. This heating is caused bythe fact that the needle enters the fabric at an angle and at a pointlocated at one side of a vertical line passing through the axis of theneedle-bar y frame fulcrum-stud and, during the feeding stroke, swingsin an arc to a )point located on the opposite side of said vertical linewhere it emerges `from the fabric at an angle. This swinging lateralmovement of the blade of the needle while in the `fabric causes theneedle- .puncture to be spread adjacent the upper and lower surfaces ofthe fabric, and this spreading of the needle-puncture by the needlecreates a pressure on the blade of the needle which increases materiallythe friction between the needle and the fabric. This increased frictiongenerates heat in the needle and, at high speeds of operation, issuflicient to render the needle unfit for continued sewing.

The primary object of the present invention is the provision in a sewingmachine of a shifting fulcrum-support for the needle-bar frame designedso that the needle enters and emerges from the -fabric in a directionsubstantially perpendicular to the surfaces of the fabric beingstitched.

With the above and other objects in view, as will hereinafter appear,the invention comprises the devices, combinations and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingsof a preferred embodiment of the invention, from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

Referring to the drawings, Fig. l is a front end elevation of the headof a sewing machine em- -bodying the invention.

Fig. 2 is a vertical section of the sewing machine head together with aportion of the bracket-arm.

Fig. 3 is an enlarged perspective view of the needle-bar-frame shiftingfulcrum and actuating mechanism therefor.

Fig. 4 is an enlarged fragmentary View of the needle and fabric of aprior machine showing, in full lines, the position of the needle justafter it `penetrates thev fabric and, in dotted lines, the position ofthe needle immediately before it iS withdrawn from the fabric. f

Fig. 5 is a view similar to Fig. 4 showing the relation between theneedle and the fabric in a sewing machine fitted with the presentimprovement.

Referring more in detail to the accompanying drawings, one embodiment ofthe invention is shown as applied to a sewing machine having abracket-arm I terminating in a head 2 overhanging a work-support, shownonly as line 3 in Figs. 1 and 2. Journaled in a conventional Torringtonneedle-bearing 4 fixed in a wal-1 5 of the bracket-arm I is a rotarymain-shaft 6 having secured at its outer end, preferably by a setscrewl, the usual counterbalanced needle-bar crank 8. Fixed in the free endof the crank 8 is a second needle-bearing 9 in which is journaled acrank-pin I8 fastened in one end of a link II pivoted at its other endupon a pin I2 integral with a split collar I3 clamped upon a needle-barI4. At its lower end the needle-bar I4 carries the usual needle I5.

The needle-bar I4, see Figs. 2 and 3, is journaled for endwisereciprocation in spaced 4bearings provided in the lugs I6 and Ilintegral with a vibratory frame I8 having an offset head I9 pivotallyhung on a fulcrum-.pin 2,3 formed upon the lower end of a crank-arm 2 I.The frame I8 is formed with the offset head to enable the needle-bar I4to be readily inserted in the .bearing lugs I6 and II. Threaded into theend of the fulcrum-pin 28 is a cap-screw 22 which prevents the offsethead. I9 of the frame I8 from shifting lengthwise of the fulcrum-pin 20.The crank-arm 2l is preferably formed integral with a short stub-shaft.23 journaled for oscillation in a bearing 24 provided in the top of themachinehead 2 rearwardly of the vertical plane containing thelongitudinal axis of the main-shaft B. Clamped by means of a screw 25upon the inner end of the stud-shaft 23 is the split upper end of arock-lever 28 provided at its lower end with a `pin 21 connected by apitman 28 to an eccentric 29 preferably cut upon the rear portion of thecounterbalanced needle-bar crank 8.

It will be understood from the above description that as the main-shaft6 is rotated, the crank-arm 2| and hence the fulcrum-pin 20 is swungabout the axis of the stub-shaft 23 in an arc, the length of Whichv isdetermined by the eccentricity of the eccentric 29. While I lhaveillustrated the eccentric 29 as having a fixed eccentricity, it isobvious that an adjustable eccentric may be substituted therefor,whereby the arc of movement of the fulcrum-pin 20 can 'be controlled toconform with the stitch-length.

As described in detail in my copending application above referred to,the frame E8 is vibrated in the line of feed in timed relation with theupper feeding mechanism and the lower feeding mechanism (not shown) ofthe machine so that the needle I will assist in advancing the materialuniformly past the stitching mechanism. Inasrnuch as the mechanism forvibrating the frame I8 is fully disclosed in my copending applicationSerial No. 267,958, only such reference will now be made to the saine aswill enable one to understand the functioning of the present Vinvention.It will be observed in Figs. 1 and 2 that the frame I8 has journaled init a presser-bar 36 and a feed-bar 3i carrying at their lower ends apresser-foot 32 and a feed-dog 33, respectively. The presser-bar 35 andthe feed-bar 3l are alternately raised and lowered in effecting afeeding action by mechanism fully described in my copending applicationand therefore will not be further described in this application.

Vibratory movement of the frame I8 in the line of feed is accomplishedby a link 34 connected at one end to a lug 35 formed on the frame I8 andat its other end to the lower end of a depending rock-lever 35 securedupon the outer end of a rock-shaft 3l journaled in suitable bosses 33cast upon the rear of the machine-head 2. Clamped upon the inner end ofthe rock-shaft 3l, see Fig. 2, is the split lower end of an upstandingrock-lever 39 connected at its upper end by a relatively short pitman 40to an adjustable eccentric II secured upon the main-shaft 8. Theadjustable eccentric 4I, the constructive features of which aredisclosed in the United States Patent to W. Myers, No. 2,128,081, issuedAug. 23, 1938, is provided so that the amplitude of vibration of theneedle in the line of feed can be made to conform with the length ofstitch to which the lower feeding mechanism is adjusted.

Referring to Figs. 2 and 3, it will be observed that the eccentric 4Iimparts to the lower end of the needle-bar frame I3 vibrations about thefulcrum-pin 2t in the line of feed, and that the eccentric 29 imparts tothe fulcrum-pin 20 oscillations about the longitudinal axis of thestubshaft 23. The eccentrics 29 and 4I are relatively timed so that thelower end of the needle-bar frame I8 and the fulcrum-pin 2t thereformove in the same direction at the same time. This simultaneous movementof the frame I8 and the pin 20 maintains the needle-bar framesubstantially vertical, so that during the work-penetrating stroke thelongitudinal axis of the needle I5 is disposed perpendicular to theupper surface S of the fabric F, as shown in Fig. 5. The position of theneedle I5 illustrated in Fig. 5 is the same during the withdrawal strokeof the needle. It will be appreciated that the friction between thefabric F and the needle I5 is at a minimum when the conditions, as shownin Fig. 5, are approached.

Fig. 4 exemplines the condition which existed in machines prior to thepresent invention. When, as in previous machines, the sewing machine isfitted with a stationary fulcrum-stud,

instead of a shifting fulcrum-pin as in the presing the feeding stroke,the needle I5 moves from the full line position into the dotted lineposition. It can be clearly seen that this lateral movement of the bladeof the needle I5 spreads the needle-puncture in the fabric adjacent theupper and lower surfaces thereof, and that this spreading actionincreases the pressure between the needle and the fabric. Obviously,this increased pressure generates excessive heat when the needle iswithdrawn from the fabric.

From the above description, it will be understood that I have provided anovel shifting fulcrum-support for the usual needle-bar-frame which isconstructed and actuated so that the friction between the reciprocatingneedle and the fabric being stitched will be reduced to a minimum. Itwill be seen also that I have provided a novel floating fulcrum-supportWhich is extremely simple in construction and which is compact andcontained entirely within the head of the machine-frame. The parts orelements of the floating fulcrum-support have been proportioned andarranged so that they may be operated at a high rate of speed withoutsetting up prohibitive vibrations.

While various parts of the mechanism cooperating with the characteristicfetures of this improvement have been shown and described somewhat indetail herein, it is evident that the specific construction andarrangement of such parts are not material to the invention and alsothat the construction and arrangement of parts of the shiftingfulcrum-support may be considerably Varied Within the scope of theinvention.

Having thus set forth the nature of the invention what I claim hereinis:

1. A sewing machine having, in combination, a bracket-arm terminating ina head, a mainshaft journaled in said bracket-arm, a frame supported onsaid head and adapted to be vibrated in the line cf feed, a needle-barjournaled for endwise reciprocatory movements in said frame, a needlecarried by said needle-bar, connections for vibrating said frame toeffect a feeding of the work, a stub-shaft journaled in said head abovethe level of said main-shaft, means fixed to said stub-Shaft andproviding a fulcrum for said frame, and means operatively connectingsaid stub-shaft to said main-shaft for shifting the fulcrum of saidframe so that the needle penetrates and emerges from the fabric in adirection substantially perpendicular to the surface of the fabric.

2. A sewing machine having, in combination, a bracket-arm terminating ina head, a mainshaft journaled in said bracket-arm, a frame supported onsaid head and adapted to bevibrated in the line of feed, a needle-barjournaled for endwise reciprocatory movements in said frame, a needlecarried by said needle-bar, connections for vibrating said frame toeffect a feeding of the work, a stub-shaft journaled in said head abovethe level of said main-shaft, a crank-arm fixed to said stub-shaft andproviding at its free end a fulcrum for said frame, and means within theconfines of said head for actuating said stub-shaftv to shift thefulcrum of said frame so that the needle penetrates and emerges from thefabric in a direction substantially perpendicular to the surface of thefabric.

3. A sewing machine having, in combination, a bracket-arm terminating ina head, a mainshaft journaled in said bracket-arm, a frame supported onsaid head and adapted to be vibrated in the line of feed, a needle-barjournaled for endwise reciprocatory movements in said frame, a needlecarried by said needle-bar, connections for Vibrating said frame toeffect a feeding of the work, a stub-shaft journaled in said head abovethe level of said main-shaft, means fixed to said stub-shaft andproviding a fulcrum for said frame, and means for actuating saidstub-shaft to shift the fulcrum of said frame so that the needlepenetrates and emerges from the fabric in a direction substantiallyperpendicular to the surface of the fabric, said last-named meansincluding a rock-lever fixed to said stubshaft, and a pitman connectedat one end to said rock-lever and at its other end to means on saidmain-shaft for actuation thereby.

4. A sewing machine having, in combination, a machine frame including abracket-arm terminating in a head, a shaft journaled in said bracket-armand extending into said head, a vibratory frame sustained upon said headand adapted to be vibrated in the line of feed, a needle-bar journaledfor endwise reciprocatory movements in said vibratory frame, a needlecarried by said needle-bar, means including a crank secured to thatportion of the shaft within said head for reciprocating said needle-bar,connections for Vibrating said vibratory frame to effect a feeding ofthe work, an oscillatable fulcrumpin located in the upper portion ofsaid head for supporting said vibratory frame, and means within theconfines of said head for oscillating said fulcrum-pin, said meansderiving its actuations from an eccentric located adjacent said crank onsaid shaft.

5. A sewing machine having, in combination, a bracket-arm terminating ina head, a mainshaft journaled in said bracket-arm, a frame having anoffset upper end sustained by said head and adapted to be vibrated, aneedle-bar journaled for endwise reciprocatory movements in said frame,a needle carried by said needlebar, connections for vibrating saidframe, a stubshaft journaled in said head above the level 0f andrearwardly of the axis of the main-shaft, means fixed to said stub-shaftand providing a fulcrum for the offset upper end of said frame, andmeans within the confines of said head operatively connecting saidstub-shaft to said main-shaft for shifting the fulcrum of said frame sothat the needle penetrates and emerges from the fabric in a directionsubstantially perpendicular to the surface of the fabric.

6. A sewing machine having, in combination, a machine frame including abracket-arm terminating in a head, a wall separating said bracketarmfrom said head, a shaft journaled in said bracket-arm and extending intosaid head, a vibratory frame sustained upon said head and adapted to bevibrated in the line of feed, a needle-bar journaled for endwisereciprocatory movements in said vibratory frame, a needle carried bysaid needle-bar, means including a needle-bar actuating crank secured tothatV portion of the shaft within said head for reciprocating saidneedle-bar, connections for Vibrating said vibratory frame to effect afeeding of the work, a. stub-shaft journaled in said head, a crank-armfixed to said stub-shaft and providing a fulcrum for said vibratoryframe, a rocklever secured to said stub-shaft, and a pitman secured atone end to said rock-lever and at its other end to an actuatingeccentric on said mainshaft, said eccentric being fast on said mainshaftbetween said needle-bar actuating crank and the wall separating saidbracket-arm from said head.

FREDERICK F. ZEIER.

